Correlation ID for local IP access

ABSTRACT

The invention relates to a home cellular base station (HeNB), comprising a radio interface (RI), to communicate with a user equipment (UE), a local interface (LI), to communicate with a local gateway (L-GW) providing access to a local IP network, a user plane interface (S1-U), to communicate with a serving gateway (SGW), and a control plane interface (S1-MME), to communicate with a control node (MME). The home cellular base station (HeNB) further comprises a selection module (SelMod) set to obtain a first correlation ID for enabling a direct user plane path between the home cellular base station (HeNB) and the local gateway (L-GW), the first correlation ID being obtained via the control plane interface (S1-MME) upon each establishment of a bearer providing access to the local IP network. 
     The invention also relates to a control node (MME), to a home subscriber server (HSS), to a direct path enablement method, and to a PDN management method.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/916,883, filed on Nov. 1, 2010, which claims priority to U.S.Provisional Patent Applications No. 61/257,434, filed on Nov. 2, 2009;No. 61/257,436, filed on Nov. 2, 2009; No. 61/257,439, filed on Nov. 2,2009; No. 61/257,442, filed on Nov. 2, 2009; No. 61/359,352, filed onJun. 29, 2010; and 61/375,016, filed on Aug. 18, 2010, the entiredisclosure of each which is hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to local IP access, also known as LIPA. LIPA is afeature of mobile communication networks, which was introduced inRelease-10 of 3GPP (see in particular section 5.7.1 of 3GPP TS 22.220V10.0.0, 2009-09).

2. Description of the Related Art

With the progressive convergence of the Internet world and of thetelecommunications world, most services that are offered on the Internetbecome available on mobile phones, and conversely voice services becomeavailable through the Internet (Voice over IP). In addition,fixed-mobile convergence aims at proposing single communication devicesable to connect both to a cellular network (e.g. when travelling) and toa local network (such as a home network, when at home, or a corporatenetwork, or a hotspot). While fixed-mobile convergence is not yet awidespread reality, many communication devices already have both a radiointerface to connect to cellular networks, and another radio interfaceto connect to a local network. Most often the two radio interfaces areused independently though (i.e. the user selects manually, eitherexplicitly or implicitly, which radio technology he wants to use).Having two radio interfaces forces the communication device to embed twodifferent radio technologies (e.g. WLAN interface and cellular radiointerface), which is more expensive, takes more space (while size andweight are important characteristics), and consumes a lot of energysince two radio interfaces need to be powered, which reduces theautonomy of the communication device (and also reduces battery life).

Cellular networks are very convenient because they offer an extremelybroad coverage (for example a GSM user can typically make phone callsfrom almost anywhere in the world). However, their bandwidth istypically rather low compared to the bandwidth offered to users of localnetworks (which are typically connected to the Internet through ratherhigh speed connections such as fiber, DSL or cable, for home networks).In addition, they are in general more expensive to use. Despite theirextensive coverage, cellular networks are not always available, forexample they are not available in certain remote locations (such ascertain rural areas, or certain very small villages), or indoorlocations not reachable by the cellular network's signals (basements,rooms surrounded by several layers of walls, etc.).

Small cellular base stations called femtocells can be used to mitigatethe unavailability of cellular networks, as long as an alternate networkaccess (typically a wired network) is available. Femtocells cantypically be simple devices installed by end users themselves.Femtocells behave like a cellular network with respect to communicationdevices (which can use their regular cellular network radio interface tocommunicate with them), and connect to a cellular network operator'score network through the alternate network access (such as Internetaccess via fiber, DSL or cable subscriptions). Femtocells can bedeveloped for any types of cellular networks technologies, for exampleWCDMA, GSM, CDMA2000, TD-SCDMA, WiMAX or LTE technologies. The 3GPPrefers to 3G femtocells as Home Node Bs (HNBs), and in LTE the properterminology for a femtocell is Home eNode B (HeNB). Femtocells are infact “home” cellular base stations.

In the context of fixed-mobile convergence of voice services, the use offemtocells is an advantageous alternative to the embedding of twodifferent radio technologies in a communication device, since thecommunication device becomes simpler to implement, can be smaller,lighter, cheaper, and have a better battery autonomy.

LIPA goes one step further and aims at providing access from acommunication device to a home-based network (for any kind of IP basedservices, not only for voice) through a femtocell. A home-based networkis in fact any kind of local network (e.g. it can be in a residential orcorporate environment, or a public hotspot), i.e. it is not necessarilya network in the home of an individual (the term “home” has to beunderstood in a broad sense, the same applies to other expressions suchas “home” cellular base station).

Although an initial specification of LIPA is already available, LIPA isstill being specified as not all issues have been addressed. LIPA istherefore the subject of standardization efforts at 3GPP. Many aspectsof LIPA are still expressed as goals to be achieved, without indicationson how to achieve these goals.

One class of LIPA solutions that are currently under study in 3GPP isreferred to as the “solutions relying on Local Packet Data Network (PDN)connection”. With this type of solutions there are several open issues.

The technical report 3GPP°TR°23.8xy v0.2.0 (“Local IP Access andSelected IP Traffic Offload”) is a study of architectural solutions forLIPA to the home-based network from a femtocell (Home NodeB or HomeeNodeB), as well as a study of architectural solutions for Selected IPTraffic Offload (SIPTO) for both femtocells and macrocells. The number23.8xy was a temporary name for the technical report on LIPA when thefirst patent application (U.S. 61/375,016) which priority is claimed inthe present patent application was filed (Nov. 2, 2009). It was laterassigned a permanent TR number by the 3GPP administration (TR 23.829).All versions of this document are stored under the permanent name on the3GPP web site. TR°23.829 v0.2.0 was updated by technical contributionssubmitted to 3GPP by the inventors of the present invention, after thepriority date of the present application. The LIPA solutions under studyin this technical report when the first priority application was filedcan be broadly summarized in two categories. The first one relates tosolutions based on traffic breakout performed within H(e)NB using alocal PDN connection, and the second one relates to solutions relying ona NAT (Network Address Translation) device.

The first category is of particular interest in the context of theinvention. The technical report was still in study phase and did notcontain any full-blown architecture figure agreed in the standard at thepriority date of the present application. Instead it contained a list ofarchitectural requirements, architectural principles and a list of openissues and proposed solutions to such issues. FIG. 1 highlights some ofthe possible architecture requirements for a LIPA solution for HeNBusing a local PDN connection according to the technical report.

The following are possible LIPA requirements according to FIG. 1. ALocal PDN Gateway (L-GW) function is collocated with the HeNB (forexample it can be embedded in the HeNB, or each function can be embeddedin a corresponding device, both devices being in the same geographicallocation). The local PDN Gateway provides direct IP access to thehome-based IP network. The Mobility Management Entity (MME) and ServingGateWay (SGW) nodes are located in the operator's Evolved Packet Core(EPC). A Security Gateway (SeGW) node is located at the edge of theoperator's core network; its role is to maintain a secure associationwith the HeNB across the IP backhaul network that is typically owned bya different provider and is therefore considered insecure. A Home router(which typically behaves as a NAT device) is located at the boundary ofthe home-based IP network and the IP backhaul network, as typicallyfound in DSL or cable access deployments today. It is also possible tohave an element (optional), depicted in FIG. 1 consisting of an externalPDN Gateway (PGW) located in the operator's core network. This elementmay be used when the user needs to access services provided by theoperator, in parallel to accessing the home-based network.

3GPP TR 23.8xy v0.2.0 identifies the following open issues with the typeof architectures described above.

One issue that needed to be solved in this context included thedefinition of signaling information needed for establishment of optimaldata path (this is referred to as “optimal routing” or “optimizedrouting information issue”). More particularly, for active UEs, therewas a need to find mechanisms to optimize the routing of the EPS/UMTSbearers used for LIPA traffic, allowing the user plane to bypass theCore SGW and SGSN. What was still unanswered was in particular the typeof information that can be used by the HeNB and the L-GW in order toestablish the direct path (“optimized routing information issue”).Specifically, for a specific UE, the kind of information that could beused by the HeNB to discriminate between uplink packets destined to thehome-based network (i.e. the L-GW) and uplink packets destined to theexternal PGW was unknown. For a specific UE, the kind of information tobe used by the HeNB to map the downlink packets received from the L-GWon the appropriate Radio Bearers was also unknown.

Another issue lies in the fact that the proposed solution is expected towork when the local breakout point (L-GW) is located in a privateaddress domain, e.g. behind a NAT gateway (this is referred to as the“NAT issue”, or “operation behind a NAT device”).

How to assist the backhaul operator to perform legal intercept isanother issue (referred to as the “Lawful Intercept issue”).

How paging works in this architecture was still an open issue, as perthe following excerpt from TR°23.8xy: “it is FFS whether IDLE modedownlink packet buffering and initiation of network triggered servicerequest procedure should be local to the H(e)NB, leading to two SGWs perUE (one in Core Network and one in H(e)NB subsystem or transportbackhaul network), which is not in line with current TS 23.401architecture principles, or whether this function should be in the CoreNetwork”.

Starting from Release 99, the 3GPP specifications make provisions foraccess to a private enterprise network (intranet) from any macro cell.This is often referred to as network-based VPN access.

With LIPA it becomes possible to access the enterprise network from afemtocell, in a way that all traffic bound to/from the enterprisenetwork is routed locally, without leaving the enterprise.

A major difference between the macro versus femto scenarios resides inthe Gateway that represents the ingress point to the intranet. In themacro scenario the terminal establishes a Packet Data Network (PDN)connection to a PDN Gateway (PGW) that is part of the operator's EvolvedPacket Core (EPC) and has pre-established a layer 2 tunnel to an ingresspoint in the intranet. In contrast, in the femtocell scenario theterminal establishes a connection to a Local Gateway (L-GW) residinginside the enterprise network.

Assuming that the same Access Point Name (APN) is used to access theenterprise network in both cases, some additional information isrequired in order to assist the EPC in selecting the right gateway,depending on whether the terminal is establishing the connection fromthe enterprise's femtocell or from somewhere else.

FIG. 2 depicts a scenario where the UE can access the Enterprise networkvia either a macro cell (eNodeB—eNB) or a femto cell (Home eNodeB—HeNB).

For VPN access via a macro cell the signaling path for PDN connectionestablishment is illustrated with an arrow going from the UE to the PGW(with two solid lines). Based on the PDN connection request receivedfrom UE, the Mobility Management Entity (MME) checks the APN requestedby UE against its subscription record in the HSS, as described in 3GPPTS 23.401 (“Evolved Packet Core for 3GPP access”). If the UE isauthorized to access the requested APN, the MME performs PGW selectionrelying on DNS resolution of the APN-FQDN i.e. a Fully Qualified DomainName that is constructed with the APN substring, as specified in 3GPP TS23.003 (“Numbering, Addressing and Identification”) and 3GPP TS 29.303(“Domain Name System Procedures; Stage 3”).

For instance, if the APN for VPN access is “companyABCvpn”, thecorresponding APN-FQDN, used for DNS resolution, will typically beconstructed as: “companyABCvpn.epc.mnc015.mcc234.3gppnetwork.org”.

In contrast, for enterprise access via LIPA, the signaling path for PDNconnection establishment is depicted with an arrow going from the UE tothe L-GW (with two dotted lines). In this case the MME would need tooverride the usual DNS resolution based on APN-FQDN and perform L-GWselection based on information other than, or in addition to, the APN.

At the time the first priority application was filed, there were twoalternatives for L-GW selection described in 3GPP TR 23.829 v1.1.0(“LIPA and SIPTO”), but there was no agreement yet which one should bestandardized. The first proposal is to have the L-GW address signaledfrom the RAN (Radio Access Network, i.e. from the HeNB). The otherproposal is to use DNS based resolution with an FQDN that contains theCSG identifier of the femtocell.

For sake of simplification, FIG. 2 makes the assumption that the ServingGateway (SGW) is located outside of the Enterprise network, even forLIPA access. While this is a possibility, it is more likely that forLIPA access the system would select a SGW that resides inside theEnterprise network (L-SGW in FIG. 3) and is collocated with the L-GW, asdepicted in FIG. 3.

The current solution is problematic when the same APN may be used toaccess the Enterprise network via both a macrocell and a femtocell.Indeed, the Mobility Management Entity (MME), which performs the PGW/LGWselection, does not know which gateway to select since it depends onwhether the terminal is requesting PDN connection establishment from theEnterprise femtocell or from somewhere else. The APN may be identifiedas being “LIPA only”, “LIPA prohibited”, or “LIPA conditional”, butwithout regard to the CSG from which the PDN connection requestoriginates.

The MME is aware whether the terminal is inside a femtocell, thanks tothe CSG ID that is provided by the RAN in all UE-associated signalingmessages. However, the user's subscription record in the HSS (at thetime the first priority application was filed) provides no informationabout possible linkage between the requested APN and the CSG ID of thefemtocell where the UE is currently residing.

If the MME selected the Enterprise L-GW whenever the UE requests theEnterprise APN from a femtocell, this would lead to the error casedepicted in FIG. 4. Namely, consider the scenario where the userrequests a PDN connection to the Enterprise APN via its home(residential) femtocell. In this case the MME must not select the L-GWresiding in the Enterprise network (arrow going from the UE to the L-GW,with two dotted lines), instead it must select the PGW (arrow going fromthe UE to the PGW, with two solid lines), in the same manner as if theUE were in a macrocell.

Table 5.7.1-1 of 3GPP TS 23.401, which describes certain HSS data, isalso useful for the understanding of the invention, and is reproducedbelow:

Field Description IMSI IMSI is the main reference key. MSISDN The basicMSISDN of the UE (Presence of MSISDN is optional). IMEI/IMEISVInternational Mobile Equipment Identity - Software Version Number MMEIdentity The Identity of the MME currently serving this MS. MMECapabilities Indicates the capabilities of the MME with respect to corefunctionality e.g. regional access restrictions. MS PS Purged from EPSIndicates that the EMM and ESM contexts of the UE are deleted from theMME. ODB parameters Indicates that the status of the operator determinedbarring Access Restriction Indicates the access restriction subscriptioninformation. EPS Subscribed Charging The charging characteristics forthe MS, e.g. normal, prepaid, Characteristics flat-rate, and/or hotbilling subscription. Trace Reference Identifies a record or acollection of records for a particular trace. Trace Type Indicates thetype of trace, e.g. HSS trace, and/or MME/ Serving GW/PDN GW trace. OMCIdentity Identifies the OMC that shall receive the trace record(s).Subscribed-UE-AMBR The Maximum Aggregated uplink and downlink MBRs to beshared across all Non-GBR bearers according to the subscription of theuser. APN-OI Replacement Indicates the domain name to replace the APN OIwhen constructing the PDN GW FQDN upon which to perform DNS queries.This replacement applies for all the APNs in the subscriber's profile.RFSP Index An index to specific RRM configuration in the E-UTRANURRP-MME UE Reachability Request Parameter indicating that UE activitynotification from MME has been requested by the HSS. CSG SubscriptionData The CSG Subscription Data is a list of CSG IDs per PLMN and foreach CSG ID optionally an associated expiration date which indicates thepoint in time when the subscription to the CSG ID expires; an absentexpiration date indicates unlimited subscription. Each subscriptionprofile contains one or more PDN subscription contexts: ContextIdentifier Index of the PDN subscription context. PDN Address Indicatessubscribed IP address(es). PDN Type Indicates the subscribed PDN Type(IPv4, IPv6, IPv4v6) APN-OI Replacement APN level APN-OI Replacementwhich has same role as UE level APN-OI Replacement but with higherpriority than UE level APN-OI Replacement. This is an optionalparameter. When available, it shall be used to construct the PDN GW FQDNinstead of UE level APN-OI Replacement. Access Point Name (APN) A labelaccording to DNS naming conventions describing the access point to thepacket data network (or a wildcard) (NOTE 6). EPS subscribed QoS profileThe bearer level QoS parameter values for that APN's default bearer (QCIand ARP) (see clause 4.7.3). Subscribed-APN-AMBR The maximum aggregateduplink and downlink MBRs to be shared across all Non-GBR bearers, whichare established for this APN. EPS PDN Subscribed The chargingcharacteristics of this PDN Subscribed context Charging Characteristicsfor the MS, e.g. normal, prepaid, flat-rate, and/or hot billingsubscription. The charging characteristics is associated with this APN.VPLMN Address Allowed Specifies whether for this APN the UE is allowedto use the PDN GW in the domain of the HPLMN only, or additionally thePDN GW in the domain of the VPLMN. PDN GW identity The identity of thePDN GW used for this APN. The PDN GW identity may be either an FQDN oran IP address. The PDN GW identity refers to a specific PDN GW. PDN GWAllocation Type Indicates whether the PDN GW is statically allocated ordynamically selected by other nodes. A statically allocated PDN GW isnot changed during PDN GW selection. PLMN of PDN GW Identifies the PLMNin which the dynamically selected PDN GW is located. Homogenous Supportof IMS Indicates whether or not “IMS Voice over PS Sessions” is Over PSSessions for MME supported homogeneously in all TAs in the serving MME.List of APN - PDN GW ID relations (for PDN subscription context withwildcard APN): APN - P-GW relation #n The APN and the identity of thedynamically allocated PDN GW of a PDN connection that is authorised bythe PDN subscription context with the wildcard APN. The PDN GW identitymay be either an FQDN or an IP address. The PDN GW identity refers to aspecific PDN GW.

The invention seeks to improve the situation.

SUMMARY OF THE INVENTION

The invention relates in particular to a home cellular base station(Home eNodeB in the LTE environment), comprising a radio interface, tocommunicate with a user equipment (such as a cellular phone), a localinterface, to communicate with a local gateway providing access to alocal IP network, a user plane interface, to communicate with a servinggateway, and a control plane interface, to communicate with a controlnode. The home cellular base station further comprises a selectionmodule set to obtain a first correlation ID for enabling a direct userplane path between the home cellular base station and the local gateway,the first correlation ID being obtained via the control plane interfaceupon each establishment of a bearer providing access to the local IPnetwork. The user plane deals with transport of actual user data, whilethe control plane consists of protocols for control and support of theuser plane functions (it deals in particular with signaling in order toestablish a communication). In the LTE context, the control plane isdefined in section 5.1.1 of 3GPP TS 23.401 V10.0.0. This home cellularbase station is advantageous, because it enables an improved routing atthe home cellular base station in a LIPA context. While the “trombone”path is needed anyway in the first place (when establishing thecommunication), once the communication is set up, the trombone path isno longer used, which is advantageous as the user plane packets do notneed to travel back and forth through the trombone.

According to a possible embodiment, the selection module of the homecellular base station is set, upon reception of a downlink IP packet onthe local interface along with a second correlation ID, to match thefirst correlation ID with the second correlation ID, in order todetermine the radio bearer on which to transmit the downlink IP packetto the user equipment through the radio interface. The first correlationID is typically received once for all during the establishment of thecommunication, while the second correlation ID is included in eachpacket, and enables the matching of correlation IDs in order to routethe packet properly. The packet is a downlink packet, i.e. a packetwhich destination is the user equipment (as opposed to uplink packetswhich originate from the user equipment). There are potentially manyradio bearers from the home cellular base station to the user equipment.This embodiment enables the selection of the proper bearer. Theembodiment is also advantageous because it does not require any complexfunction such as DL-TFT (downlink traffic flow template) which is a kindof packet filter, thanks to the simple correlation ID. Such complextasks (such as tasks requiring layer 3 capabilities, as opposed toconventional layer 2 capabilities of an HeNB) can remain, for example,in the PGW (L-GW in LIPA) and/or in the UE, for example.

In an alternative embodiment, the selection module of the home cellularbase station is set to send the first correlation ID to the localgateway through the local interface upon each establishment of a bearerproviding access to the local IP network, and to delegate to the localgateway the matching of the first correlation ID with a secondcorrelation ID identified by the local gateway during bearer binding ofa downlink IP packet, in order to determine the radio bearer on which totransmit the downlink IP packet to the user equipment through the radiointerface. The second correlation ID is identified within the localgateway, while the first correlation ID is received in the home cellularbase station. This embodiment is advantageous as it allows the localgateway to perform the matching on behalf of the home base station, andthen to inform the home base station accordingly. It would be possibleto send the first and second correlation IDs to a third party (otherthan the home cellular base station and the local gateway) and to letthe third party carry out the matching. In all variants, it is possibleto inform the home cellular base station of the matching by linking thepacket to the first correlation ID (as matched). Since the home cellularbase station knows the first correlation ID and is able to link it to aparticular bearer (the bearer that was created during establishment ofthe communication at stake), the home cellular base station can send thepacket on the proper bearer. It is noted that with GTP, an EPS bearerencompasses different bearers, such as a radio bearer between the UE andthe HeNB, the S1 bearer between the eNB and the SGW, and the S5/S8bearer between the SGW and the PGW (or L-GW in the LIPA case). There isa one to one relationship between each of those bearers. While in stateof the art, the HeNB maps only the S1 bearer and the radio bearer, withthe invention it is possible to map inside the HeNB the radio bearer,the S1 bearer, and the S5 bearer (thanks to the S5 PGW TEID correlationID for example). There are different ways to carry out a mapping, forexample the radio bearer can be mapped directly to the S5 bearer, or themapping can be done through the intermediate S1 bearer. All bearerswhich are associated together can be represented by different items(e.g. bearer IDs) in a line in a table, so that any element in the linecan be mapped with any other element in the line (the mapping beingbased on the fact that the elements belong to the same line).

According to a possible embodiment, the selection module of the homecellular base station is set to check, upon reception of an uplink IPpacket on a radio bearer of the radio interface, the presence of thefirst correlation ID for said radio bearer. The uplink IP packet canthen be transmitted through the local interface if the first correlationID is present, and through the user plane interface if the firstcorrelation ID is not present. In particular, in the LTE context, it ispossible to implement this embodiment in the following manner. Duringbearer establishment, the MME can provide the user equipment with thepacket filters for selecting the bearer, and can provide the HeNB withthe correlation ID for the bearer that is being established. When theuser equipment sends a packet (it is an uplink packet), it applies thepacket filter in order to use the proper bearer. Then the packet isreceived at the home cellular base station, which maintains a list ofbearers and associated first correlation ID (if any). So the homecellular base station can check whether there is a correlation ID forthat specific packet (depending on the specific bearer on which it wassent) or not. Accordingly, the home cellular base station can send thepacket either to the local gateway or to the Serving GateWay. Thisembodiment is advantageous since it enables an improved routing ofuplink packets.

According to a possible embodiment, the radio bearer can correspond to aGTP bearer on the local gateway, and the first correlation ID comprisesa PGW TEID (it can actually be a PGW TEID). A TEID (Tunnel EndpointIdentifier) unambiguously identifies a tunnel endpoint in a receivingGTP-U (GPRS Tunnelling Protocol—User) or GTP-C (GPRS TunnellingProtocol—Control) protocol entity. The receiving side of a GTP tunneltypically assigns a TEID value locally for the transmitting side to use.TEID values are typically exchanged between tunnel endpoints using GTP-Cmessages (or RANAP—Radio Access Network Application Part) in the UTRAN(UMTS terrestrial Radio Access Network). Since we are in LIPA, the PGW(PDN Gateway) is in fact the local gateway collocated with the homecellular base station. The PGW TEID can be sent from the serving gatewayto the MME (through S11) and then from the MME to the home cellular basestation HeNB through S1-MME, during bearer establishment. Then the PGWTEID can be used as a first correlation ID in the home cellular basestation. This is advantageous since constitutes an efficient solution inthe context of a protocol (the GTP protocol) that is likely to be theprevalent protocol.

Alternatively, the radio bearer can correspond to a PMIP tunnel on thelocal gateway, and the first correlation ID can comprise (or evenconsist of) a PGW GRE key. The EPS architecture defined in 3GPP TS23.401 (“Evolved Packet Core architecture for 3GPP accesses; Stage 2”)allows for two different protocols on S5: GTP (defined in 3GPP TS29.274, “GPRS Tunnelling Protocol; Stage 3”) and PMIP (defined in 3GPPTS 29.275 “Proxy Mobile IP protocol; Stage 3”). The same protocol choicecould be available in LIPA environments. In LTE, with PMIP, the packetfiltering (an “intelligent” task) is not carried out in the PGW (unlikein the GTP case) but in the SGW (serving gateway). PMIP does not use theterm “bearer” but implements an equivalent mechanism based onencapsulation. Therefore identifying the “bearers” with PMIP (althoughthey are not called the same way) is still required. Accordingly, it ispossible to send the PGW GRE from the SGW to MME through S11, and tosend the PGW GRE from the MME to the HeNB through S1-MME, in order touse PGW GRE as a correlation ID.

The invention also relates to a control node (such as an MME in LTEcontext), comprising a PDN management module for checking whether agiven packet data network connection is established for local IP access,and upon positive check (i.e. if the connection which establishment isrequested is supposed to be a LIPA connection), for sending a firstcorrelation ID to a home cellular base station which is managing thispacket data network connection, wherein the first correlation ID is usedfor enabling a direct user plane path between the home cellular basestation and a collocated local gateway providing access to a local IPnetwork. Such control node is useful to improve the routing of datapackets by shortening the path through which they have to travel (nomore tromboning).

The invention also relates to a control node comprising an authorizationmodule arranged for receiving an Access Point Name (APN) associated withthe packet data network connection and for checking this APN against alist of authorized APNs for the closed subscriber group (CSG) associatedwith the home cellular base station. This is advantageous since itprevents a user who is authorized to access a given APN from a given CSG(e.g. corporate CSG) to access this APN from a CSG from which he is notauthorized to access this APN (e.g. a personal CSG, at home). This isadvantageous as it prevents undesired establishment of PDN connections,especially connection from a home user to his employer's intranet viaLocal IP Access, while at home. Such attempts will simply fail becauseLocal IP Access to the employer's intranet is possible only when theuser is located inside the corporate CSG.

It is possible to combine the features of both control nodes embodimentsabove, that is to first check in the control node whether the PDNconnection is authorized based on the APN and CSG, and then, ifauthorized, to check whether it is established for LIPA, and accordinglyto send a correlation ID.

The invention also relates to a home subscriber server (HSS) comprisinga local IP access management module set to provide a control node (suchas an MME in an LTE context) with local IP access configurationinformation. In particular, the local IP access configurationinformation may comprise for each CSG, the list of access point namescorresponding to the packet data networks accessible via local IP accessfrom said CSG. This home subscriber server can replace state of the arthome subscriber servers and work in conjunction with the control nodesaccording to the invention by supplying them with useful information, inparticular APN and CSG information, which is useful in particular incontrolling that only proper LIPA connections are established.

The invention also relates to a direct path enablement method comprisinga step of obtaining, in a home cellular base station, a firstcorrelation ID for enabling a direct user plane path between the homecellular base station and a local gateway providing access to a local IPnetwork. The first correlation ID is obtained via a control planeinterface (such as S1-MME in LTE) of the home cellular base station uponeach establishment of a bearer providing access to the local IP network.This improves the routing of data packets.

The method may comprise a step of receiving a downlink IP packet andidentifying a second correlation ID by the local gateway during bearerbinding of the downlink IP packet, and a step of matching the firstcorrelation ID with the second correlation ID, in order to determine theradio bearer on which to transmit the downlink IP packet to a userequipment through a radio interface of the home cellular base station.

The method may, when the downlink IP packet is received on a localinterface of the home cellular base station, comprise carrying out thematching step the home cellular base station. Alternatively, the methodmay comprise sending the first correlation ID from the home cellularbase station to the local gateway through a local interface of the homecellular base station upon each establishment of a bearer providingaccess to the local IP network, and matching the first correlation IDwith the second correlation ID by the local gateway on behalf of thehome cellular base station.

The method may comprise a step of receiving an uplink IP packet on aradio bearer of a radio interface of the home cellular base station, astep of checking the presence of the first correlation ID for said radiobearer, and a step of transmitting the uplink IP packet through a localinterface of the home cellular base station if the first correlation IDis present, and through the user plane interface (such as S1-U) of thehome cellular base station if the first correlation ID is not present.

The invention also relates to a PDN management method comprising a stepof providing local IP access configuration information from a homesubscriber server to a control node, in order to assist the control nodein establishment of a packet data network connection.

In particular, the local IP access configuration information maycomprise information indicating, for each closed subscriber group, thelist of access point names corresponding to the packet data networksaccessible via local IP access from said closed subscriber group.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects and advantages of the invention will become apparent fromthe following detailed description of specific embodiments of theinvention, and the accompanying drawings, in which:

FIG. 1 represents an example of LIPA solution for HeNB using local PDNconnection;

FIG. 2 represents an enterprise access from a macrocell versus anenterprise access from a femtocell;

FIG. 3 represents an enterprise access from a macrocell versus anenterprise access from a femtocell, which is an alternative to FIG. 2with L-SGW;

FIG. 4 represents an error case in which no enterprise access should beallowed from the femtocell;

FIG. 5 represents an optimized routing information with S5-GTP;

FIG. 6 represents an optimized routing information with S5-PMIP;

FIG. 7 represents a User plane protocol stacks with GTP-based S5;

FIG. 8 represents an attach procedure (from 3GPP TS 23.401 “EvolvedPacket Core architecture for 3GPP accesses; Stage 2”) with additionalparameters in step°17;

FIG. 9 represents a Dedicated Bearer Activation Procedure (from 3GPP TS23.401 “Evolved Packet Core architecture for 3GPP accesses; Stage 2”)with additional parameters in step°4;

FIG. 10 represents a UE requested PDN connectivity (from 3GPP TS 23.401“Evolved Packet Core architecture for 3GPP accesses; Stage 2”) withadditional parameters in step°7;

FIG. 11 represents an S1-based handover (from 3GPP TS 23.401 “EvolvedPacket Core architecture for 3GPP accesses; Stage 2”) with additionalparameters in step°5;

FIG. 12 represents a UE triggered Service Request procedure (from 3GPPTS 23.401 “Evolved Packet Core architecture for 3GPP accesses; Stage 2”)with additional parameters in step°4;

FIG. 13 represents a Network triggered Service Request procedure (from3GPP TS 23.401 “Evolved Packet Core architecture for 3GPP accesses;Stage 2”) with additional parameters in step°2 a;

FIG. 14 represents an IKEv2 signaling for establishment of IPsec tunnelbetween HeNB and SeGW (from 3GPP TS 33.320 v1.0.0 “3GPP Security Aspectof Home NodeB and Home eNodeB”);

FIG. 15 represents a UE Context Modification procedure (from 3GPP TS36.413 “S1 Application Protocol (S1-AP)”) with additional parameters;

FIG. 16 represents the equivalent LIPA solution for HNB using local PDNconnection;

DETAILED DESCRIPTION OF THE INVENTION

As shown on FIG. 1, when the communication device, which is called UserEquipment or simply UE in the LTE context, is actively communicatingwith the home-based network, the traffic follows a short-cut path, asfollows. Uplink packets sent by the UE and received by the HeNB areforwarded directly to the collocated L-GW function, which relays themtowards the home-based network. Downlink packets received by the L-GWfunction are forwarded directly to the collocated HeNB, which relaysthem on the radio interface towards the UE.

In other words, when the UE is engaged in active communication, there isno circular traffic exchange across the S1-U and S5 reference points,often referred to as traffic “tromboning”.

The upper part of FIG. 5 shows the user-plane information, stored invarious EPS nodes according to state of the art, that is used for packetforwarding inside a network with GTP-based S5 (termed S5-GTP). Thestored information is described as follows. S1 eNB TEID is a tunnelendpoint identifier used in the GTP-U protocol on S1, assigned by eNB,stored in eNB and SGW. S1 SGW TEID is a tunnel endpoint identifier usedin the GTP-U protocol on S1, assigned by SGW, stored in eNB, SGW andMME. S5 SGW TEID is a tunnel endpoint identifier used in the GTP-Uprotocol on S5, assigned by SGW, stored in SGW and PGW. S5 PGW TEID is atunnel endpoint identifier used in the GTP-U protocol on S5, assigned byPGW, stored in SGW, PGW and MME.

The lower part of FIG. 5 focuses on the corresponding LIPA scenario,according to an embodiment of the invention, in which the PGW (termedL-GW, for local gateway) becomes collocated with the HeNB. As seen fromFIG. 5, state of the art L-GW function and the HeNB function of thecollocated node share no information in common.

In order to allow the combined HeNB/L-GW node to identify the mappingbetween IP packets and corresponding EPS bearers (or E-RABs) it isproposed here to use the S5 PGW TEID parameter as follows.

S5 PGW TEID is known by the MME and is signaled to HeNB across S1-MME aspart of the E-RAB context setup in messages like INITIAL CONTEXT SETUPREQUEST or E-RAB SETUP REQUEST, etc. This S5 PGW TEID, abbreviated PGWTEID, can therefore be used as a first correlation ID in an embodimentof the invention.

In a possible embodiment, for downlink packets, the L-GW functionperforms a usual bearer binding onto EPS bearers, which results inidentifying the underlying S5 PGW TEID parameter. The L-GW function thenpasses (internally) the S5 PGW TEID parameter to the HeNB function alongwith the IP packet. This is an internal operation in the sense that theL-GW and the HeNB are collocated (so the information does not have totravel through an external network). The interface between the L-GW andthe HeNB can however rely on a network protocol, in order (for example)to reuse software bricks developed for a regular PGW which is notcollocated with the HeNB.

The HeNB function maps S5 PGW TEID to the corresponding S1 eNB TEID andthus identifies the appropriate E-RAB context and the correspondingRadio Bearer on which to send the packet to the UE.

In a possible embodiment, for uplink packets, the very presence of theS5 PGW TEID parameter in the Radio Bearer context indicates that thepacket should be forwarded to the L-GW function, rather than over S1-U(user plane interface). The S5 PGW TEID parameter may be passed(internally) along with the IP packet; this could be used by the L-GWfunction e.g. to perform bearer binding verification.

FIG. 6 considers the same issue with PMIP-based S5 (S5-PMIP) instead ofGTP-based S5.

The upper part of FIG. 6 shows the user-plane information, stored invarious EPS nodes according to a known architecture, that is used forpacket forwarding inside the network with S5-PMIP. The storedinformation related to S5 is different from the S5-GTP case (bolditalics are used in FIG. 6 for PMIP-specific information) and isdescribed as follows:

S5 SGW GRE is the GRE key used in the GRE encapsulated IP packets on S5,assigned by SGW, stored in SGW and in PGW. GRE stands for GenericRouting Encapsulation and is a tunneling protocol that can encapsulate awide variety of network layer protocol packet types inside IP tunnels.S5 PGW GRE is the GRE key used in the GRE encapsulated IP packets on S5,assigned by PGW, stored in SGW, PGW and MME.

The lower part of FIG. 6 focuses on the corresponding LIPA scenario inwhich the PGW (termed L-GW) becomes collocated with the HeNB. As seenfrom FIG. 6, the L-GW function and the HeNB function of the collocatednode share no information in common. In order to allow the combinedHeNB/L-GW node to identify the mapping between IP packets andcorresponding EPS bearers (or E-RABs) it is proposed here to use the S5PGW GRE parameter as follows.

S5 PGW GRE is known by the MME and is signaled to HeNB across S1-MME aspart of the E-RAB context setup in messages such as INITIAL CONTEXTSETUP REQUEST or E-RAB SETUP REQUEST, etc.

For downlink packets, the L-GW function identifies the S5 PGW GRE keycorresponding to the local PDN connection for this UE. The L-GW functionpasses (internally) the S5 PGW GRE parameter to the HeNB function alongwith the IP packet. The HeNB function maps S5 PGW GRE to thecorresponding S1 eNB TEID and thus identifies the appropriate E-RABcontext and the corresponding Radio Bearer.

For uplink packets, the very presence of the S5 PGW GRE parameter in theRadio Bearer context indicates that the packet should be forwarded tothe L-GW function, rather than over S1-U. The proposed solution for PMIPworks only in case there is only one EPS bearer per PDN connection (i.e.the default EPS bearer), which is expected to be the most common LIPAdeployment scenario.

Some of the above embodiments or their variants can be integrated in3GPP standards, for example in the following manner.

FIG. 8 describes an Attach procedure according to 3GPP TS 23.401(“Evolved Packet Core architecture for 3GPP accesses; Stage 2”) modifiedaccording to an embodiment of the invention, in which an S5 PGW TEIDparameter (for S5-GTP) or an S5 PGW GRE parameter (for S5-PMIP) is addedin step°17 of the procedure (i.e. INITIAL CONTEXT SETUP REQUEST messageof the S1-AP protocol as specified in 3GPP TS 36.413 “S1 ApplicationProtocol (S1-AP)”). The attach/accept is based on NAS(Non-Access-Stratum, a functional layer in the Wireless Telecom protocolstack between Core Network and User Equipment), i.e. a differentprotocol (the initial context setup request is based on S1-AP), but ispiggy backed on the S1 control message. In step 17, the MME decides toattach the correlation ID only if this is necessary. If the connectionwhich establishment is requested is not a LIPA connection, nocorrelation ID is needed. In step 11, whether the requested connectionis LIPA or not, it may be determined that the current CSG is notauthorized for LIPA, and should accordingly be denied (as LIPA). It isuseful to distinguish the authorization of a LIPA connection from themere request of a LIPA connection.

FIG. 9 shows a Dedicated Bearer Activation procedure from 3GPP TS23.401, modified according to an embodiment of the invention, in whichan S5 PGW TEID parameter is added in step°4 of the procedure (i.e.BEARER SETUP REQUEST message of the S1-AP protocol). In this caseapplies only S5-GTP is applicable (no PMIP).

FIG. 10 shows an UE Requested PDN Connectivity procedure from 3GPP23.401, modified according to an embodiment of the invention, in whichan S5 PGW TEID parameter (for S5-GTP) or an S5 PGW GRE parameter (forS5-PMIP) is added in step°7 of the procedure (i.e. BEARER SETUP REQUESTmessage of the S1-AP protocol).

FIG. 11 shows an S1-based Handover procedure from 3GPP 23.401, modifiedaccording to an embodiment of the invention, in which an S5 PGW TEIDparameter (for S5-GTP) or an S5 PGW GRE parameter (for S5-PMIP) is addedin step°5 of the procedure (i.e. HANDOVER REQUEST message of the S1-APprotocol).

FIG. 12 is the Service Request procedure from 3GPP 23.401, modifiedaccording to an embodiment of the invention, in which an S5 PGW TEIDparameter (for S55-GTP) or the S5 PGW GRE parameter (for S5-PMIP) isadded in step°4 of the procedure (i.e. INITIAL CONTEXT SETUP REQUESTmessage of the S1-AP protocol).

In order to address the “NAT issue”, as shown on FIG. 1, the S1-MME andS1-U reference points can be secured by tunneling inside an IPsectunnel, established between the HeNB and the SeGW, as specified in 3GPPTS 33.320 v1.0.0 “3GPP Security Aspect of Home NodeB and Home eNodeB”.On top of this standardized security mechanism, FIG. 1 proposes that theS5 reference point (between SGW and L-GW) be also secured by tunnelinginside the same IPsec tunnel established between the HeNB and the SeGW.

Such an arrangement provides a convenient solution to the L-GW functionreachability. Namely, the L-GW function resides in the home network anduses a private IP address. As such, it is not easily reachable from theoutside e.g. for signaling transactions initiated by the SGW over S5.

By tunneling S5 inside an IPsec tunnel, the L-GW function becomesreachable via an IP address assigned from the Evolved Packet Corenetwork. In theory, S5 could be tunneled in a different IPsec tunnelthan the one used for S1, however, it is advantageous not to do it.Indeed, contrary to the IPsec tunnel for S1 that is up and runningpermanently, the S5 IPsec tunnel is needed only when the femtocell userneeds access to the home-based network. In addition, opening two IPsectunnels could typically require twice more credentials (differentcredentials are typically required to authenticate parties throughdifferent IPsec tunnels), and could pose scalability issues whileincreasing complexity. Reusing the same credentials would be conceivablein certain instances but may lower the security, depending on thespecific situation.

When using S5-GTP, there are two instances of the GTP-U protocol insidethe IPsec tunnel: GTP-U over S1-U and GTP-U over S5. This creates anissue as explained in FIG. 7.

FIG. 7 shows the user plane protocol stacks on S1-U and S5. The GTP-Uprotocol is transported over UDP and has a well-known UDP port number(port number 2152). If the combined HeNB/L-GW node uses the same IPaddress for both S1-U and S5, the SGW will be unable to discriminatepackets flowing on S1-U from packets flowing on S5.

In order to allow the SGW to discriminate packets flowing on S1-U frompackets flowing on S5, a possible embodiment of the combined HeNB/L-GWnode uses two different addresses: one for the HeNB function and theother one for the L-GW function. For example, an IPsec tunnel betweenHeNB and SeGW is established, in accordance with 3GPP TS 33.320 v1.0.0(“3GPP Security Aspect of Home NodeB and Home eNodeB”) with the IKEv2protocol (IETF RFC 4306 “Internet Key Exchange IKEv2 protocol”).According to a possible embodiment, it is proposed to take advantage ofthe fact that the IKEv2 protocol allows the “initiator” to requestmultiple “internal IP addresses” via the CFG_REQUEST configurationpayload during the initial IKEv2 exchange (see clause 3.15.1 in RFC4306). In the “initiator” role, the combined HeNB/L-GW node may thenrequest at least two internal IP addresses and assign one to the HeNBand another one to the L-GW functions. Upon setup of the S1-MMEinterface, the L-GW address is passed to the MME as part of the S1 SETUPREQUEST message defined in 3GPP TS 36.413 (“S1 Application Protocol(S1-AP)”). Alternatively, the L-GW address can be passed in the INITIALUE MESSAGE message defined in TS 36.413, however this is typically lessefficient than sending it in the S1 SETUP REQUEST message.

Alternatively, it is possible to have the HeNB function and the L-GWfunction share the same IP address, and to configure the TEID assignmentlogic in the HeNB and the L-GW so that the same TEID is never usedsimultaneously on both S5 and S1-U. For instance this can be achieved bydividing the TEID value range into two disjoint subranges that arereserved for the HeNB and L-GW function, respectively. The Subranges arepreferably contiguous, however any subrange is in principle acceptable,for example one could arbitrarily decide that odd TEIDs are for S5 andeven TEIDs are for S1-U, or vice versa. The entity assigning the TEIDsis not the SGW, but the HeNB/L-GW.

When PMIP is used on S5 it is also possible to use two different IPaddresses for the HeNB and the L-GW function, but this is not required,because the user plane protocols on S1-U and S5 are different (GTP-U vsGRE encapsulated IP packets), so it is possible to discriminate betweenthe data streams even with a single IP address. Having two IP addressesmay however simplify the discrimination between the two protocols.

Some of the above embodiments or their variants can be integrated in3GPP standards, for example as depicted on FIG. 14, which shows theIKEv2 signaling for establishment of IPsec tunnel between HeNB and SeGWfrom 3GPP TS 33.320 v1.0.0 (“3GPP Security Aspect of Home NodeB and HomeeNodeB”), modified according an embodiment of the invention so that thecall flow involves a CFP_REQUEST configuration payload in step°4 of theprocedure modified to request two “internal” IP addresses: one for theHeNB and another one for the L-GW functions. Similarly, the CSF_REPLY instep°7 is used by the SeGW to provide the requested IP addresses.

Regarding the “Lawful Intercept issue”, a problem lies in the fact thatthe packets flowing on the short-cut path (in the absence of tromboning)are outside of the reach of the EPC operator.

In order to assist Lawful Intercept it is proposed here, based on EPCrequest, to send a copy of every IP packet (exchanged across theshort-cut path) on S1-U and S5, respectively. The details of thisprocedure are as follows. Upon establishment of the local PDN connectionor at any time afterwards, the MME may request from the HeNB (e.g. inINITIAL CONTEXT SETUP REQUEST message or E-RAB SETUP REQUEST message orUE CONTEXT MODIFICATION REQUEST message) to send a copy of every uplinkpacket on S1-U. Each packet copy is tagged as such via a new flag in theGTP-U encapsulation header, so that it can be consumed at the SGWwithout being forwarded on S5. Upon establishment of the local PDNconnection or at any time afterwards, the MME may request from the L-GWfunction (e.g. Create Session Request message and Modify Bearer Requestwith S5-GTP; Proxy Binding Update with S5-PMIP) to send a copy of everydownlink packet on S5. Each packet copy is tagged as such via a new flagin the GTP-U or GRE encapsulation header, so that it can be consumed atthe SGW without being forwarded on S1-U.

Given the collocation of the HeNB function and L-GW function in the samenode, it may suffice to activate the Lawful Intercept feature on theS1-MME side only. The HeNB function in the combined HeNB/L-GW node canthen internally request the activation of the Lawful Intercept featurefrom the collocated L-GW function.

Some of the above embodiments or their variants can be integrated in3GPP standards, for example as depicted on FIG. 15, which shows the UEContext Modification procedure from 3GPP TS 36.413 (“S1 ApplicationProtocol (S1-AP)”), modified according to an embodiment of the inventionso that the flow involves an UE CONTEXT MODIFICATION REQUEST messageused to turn the Lawful Intercept feature on or off. The HeNB functionin the combined HeNB/L-GW function then internally notifies the L-GWfunction to activate or deactivate the Lawful Intercept feature.

According to a possible embodiment, a solution is proposed to optimizepaging for multiple PDN connections.

Paging may work in the manner proposed in 3GPP S2-095348 “Open issuesand solution for SIPTO and LIPA services”. In particular, when UE is inIdle mode there is no direct path between L-GW and the HeNB; thedownlink packets are consequently sent to the SGW across S5. SGW buffersthe downlink packets and triggers the paging procedure via the MME;there are no modifications compared to how paging works in the originalEPC architecture described in 3GPP TS 23.401 (“Evolved Packet Corearchitecture for 3GPP accesses; Stage 2”). When UE responds to pagingand enters Connected mode, the direct path between HeNB and L-GW becomesactive. All future packet exchanges between HeNB and L-GW follow thedirect path, until the UE is moved to Idle mode again.

As illustrated in FIG. 1, the UE may have an established external PDNconnection in addition to the LIPA PDN connection. When downlink dataarrive at the SGW either from the L-GW or from the external PGW, and theUE is in IDLE mode, the SGW sends a Downlink Data Notification (DDN)message to the MME triggering the latter to start paging the UE.

Presently the DDN message contains no information about the PDNconnection on which the downlink data are arriving.

In certain LIPA scenarios it may be beneficial to inform the MME aboutthe underlying PDN connection so that it can make a finer decision.

A possible scenario in which the invention can be advantageous is thefollowing. A User's femtocell is in the same Tracking Area as thesurrounding macrocell. Therefore the MME does not always know whetherthe idle UE is camping on the femtocell or on the macrocell. Whendownlink data arrive on the LIPA PDN connection and if the user is notallowed to access his home network from a macrocell, the UE shouldideally be paged only in the femtocell rather than in the whole TrackingArea. This can be achieved by indicating the PDN connection in theDownlink Data Notification message.

Another possible scenario in which the invention can be advantageous isthe following. A femtocell (e.g. in a house) offers a spotty coverage(e.g. a big house or thick walls). Quite often the user goes out offemtocell coverage in which case the communication is handed over to amacrocell. When in macrocell the user is not allowed to access his homenetwork, but is naturally allowed access to the external PDN connection.Despite the fact the user cannot access his home network, the MME doesnot release the LIPA PDN connection in order to avoid unnecessarysignaling. When re-selecting between femtocell and macrocell coverage,the user sends a Tracking Area Update so that the MME knows whether theidle UE is in femtocell or macrocell coverage.

When downlink data arrive on the local network the MME should not pagethe UE if the UE is in a macro cell. This can be achieved by indicatingthe PDN connection in the Downlink Data Notification message.

Some of the above embodiments or their variants can be integrated in3GPP standards, for example in the manner illustrated on FIG. 13. FIG.13 is a Network triggered Service Request procedure from 3GPP 23.401,modified according to an embodiment of the invention, in which a LinkedEPS Bearer ID (LBI) parameter is added in step°2 a of the procedure(i.e. DOWNLINK DATA NOTIFICATION message of the GTPc-v2 protocol definedin 3GPP TS 29.274 “GPRS Tunneling Protocol; Stage 3”).

According to an embodiment of the invention, user subscriptioninformation stored in the HSS is enhanced by associating the Packet DataNetwork's (PDN's) Access Point Name (APN) with the Closed SubscriberGroup identifier (CSG ID) of the femtocell(s) from which the user isallowed to establish a PDN connection according to the Local IP Access(LIPA) principles. Specifically, the enhanced user's subscriptioninformation allows the Mobility Management Entity (MME) to override theusual PDN Gateway (PGW) selection algorithm with a LIPA-specific LocalGateway (L-GW) selection algorithm.

As seen from Table 5.7.1-1 of 3GPP TS 23.401, which describes theinformation storage in HSS according to state of the art, the CSGSubscription Data i.e. a list of CSG IDs to which the user can havefemtocell access, is specified outside of the PDN subscription contexts.However, in order to avoid error cases like the one described in FIG. 4,it is proposed, in a possible embodiment, that the APN that can be usedfor LIPA access be explicitly associated with the CSG IDs from which theuser can access the corresponding PDN in LIPA fashion.

In a possible embodiment, it is proposed to enhance the user'ssubscription record in the HSS as indicated in the table below. Namely,for each Access Point Name (APN) that is associated with a Packet DataNetwork (PDN) that can be accessed via Local IP Access (LIPA) it isproposed to define an optional parameter “CSG IDs for Local IP Access”indicating the CSG IDs of femtocells from which this PDN can be accessedin LIPA fashion. The enhancements are indicated in bold italics.

Field Description IMSI IMSI is the main reference key. MSISDN The basicMSISDN of the UE (Presence of MSISDN is optional). IMEI/IMEISVInternational Mobile Equipment Identity - Software Version Number MMEIdentity The Identity of the MME currently serving this MS. MMECapabilities Indicates the capabilities of the MME with respect to corefunctionality e.g. regional access restrictions. MS PS Purged from EPSIndicates that the EMM and ESM contexts of the UE are deleted from theMME. ODB parameters Indicates that the status of the operator determinedbarring Access Restriction Indicates the access restriction subscriptioninformation. EPS Subscribed Charging The charging characteristics forthe MS, e.g. normal, prepaid, Characteristics flat-rate, and/or hotbilling subscription. Trace Reference Identifies a record or acollection of records for a particular trace. Trace Type Indicates thetype of trace, e.g. HSS trace, and/or MME/ Serving GW/PDN GW trace. OMCIdentity Identifies the OMC that shall receive the trace record(s).Subscribed-UE-AMBR The Maximum Aggregated uplink and downlink MBRs to beshared across all Non-GBR bearers according to the subscription of theuser. APN-OI Replacement Indicates the domain name to replace the APN OIwhen constructing the PDN GW FQDN upon which to perform DNS queries.This replacement applies for all the APNs in the subscriber's profile.RFSP Index An index to specific RRM configuration in the E-UTRANURRP-MME UE Reachability Request Parameter indicating that UE activitynotification from MME has been requested by the HSS. CSG SubscriptionData The CSG Subscription Data is a list of CSG IDs per PLMN and foreach CSG ID optionally an associated expiration date which indicates thepoint in time when the subscription to the CSG ID expires; an absentexpiration date indicates unlimited subscription. Each subscriptionprofile contains one or more PDN subscription contexts: ContextIdentifier Index of the PDN subscription context. PDN Address Indicatessubscribed IP address(es). PDN Type Indicates the subscribed PDN Type(IPv4, IPv6, IPv4v6) APN-OI Replacement APN level APN-OI Replacementwhich has same role as UE level APN-OI Replacement but with higherpriority than UE level APN-OI Replacement. This is an optionalparameter. When available, it shall be used to construct the PDN GW FQDNinstead of UE level APN-OI Replacement. Access Point Name (APN) A labelaccording to DNS naming conventions describing the access point to thepacket data network (or a wildcard) (NOTE 6).

EPS subscribed QoS profile The bearer level QoS parameter values forthat APN's default bearer (QCI and ARP) (see clause 4.7.3).Subscribed-APN-AMBR The maximum aggregated uplink and downlink MBRs tobe shared across all Non-GBR bearers, which are established for thisAPN. EPS PDN Subscribed The charging characteristics of this PDNSubscribed context Charging Characteristics for the MS, e.g. normal,prepaid, flat-rate, and/or hot billing subscription. The chargingcharacteristics is associated with this APN. VPLMN Address AllowedSpecifies whether for this APN the UE is allowed to use the PDN GW inthe domain of the HPLMN only, or additionally the PDN GW in the domainof the VPLMN. PDN GW identity The identity of the PDN GW used for thisAPN. The PDN GW identity may be either an FQDN or an IP address. The PDNGW identity refers to a specific PDN GW. PDN GW Allocation TypeIndicates whether the PDN GW is statically allocated or dynamicallyselected by other nodes. A statically allocated PDN GW is not changedduring PDN GW selection. PLMN of PDN GW Identifies the PLMN in which thedynamically selected PDN GW is located. Homogenous Support of IMSIndicates whether or not “IMS Voice over PS Sessions” is Over PSSessions for MME supported homogeneously in all TAs in the serving MME.List of APN - PDN GW ID relations (for PDN subscription context withwildcard APN): APN - P-GW relation #n The APN and the identity of thedynamically allocated PDN GW of a PDN connection that is authorised bythe PDN subscription context with the wildcard APN. The PDN GW identitymay be either an FQDN or an IP address. The PDN GW identity refers to aspecific PDN GW.

This is advantageous, since it enables the network (through the HSS),rather than the user equipment, to determine the address of the L-GW,which is a preferred scenario.

In an alternative embodiment, for each CSG ID in the CSG SubscriptionData record that can be used for Local IP Access (LIPA) it is proposedto associate the Access Point name (APN) of the Packet Data network(PDN) that can be accessed in LIPA fashion. This is shown on the tablebelow (enhancements in bold italics).

Field Description IMSI IMSI is the main reference key. MSISDN The basicMSISDN of the UE (Presence of MSISDN is optional). IMEI/IMEISVInternational Mobile Equipment Identity - Software Version Number MMEIdentity The Identity of the MME currently serving this MS. MMECapabilities Indicates the capabilities of the MME with respect to corefunctionality e.g. regional access restrictions. MS PS Purged from EPSIndicates that the EMM and ESM contexts of the UE are deleted from theMME. ODB parameters Indicates that the status of the operator determinedbarring Access Restriction Indicates the access restriction subscriptioninformation. EPS Subscribed Charging The charging characteristics forthe MS, e.g. normal, prepaid, Characteristics flat-rate, and/or hotbilling subscription. Trace Reference Identifies a record or acollection of records for a particular trace. Trace Type Indicates thetype of trace, e.g. HSS trace, and/or MME/ Serving GW/PDN GW trace. OMCIdentity Identifies the OMC that shall receive the trace record(s).Subscribed-UE-AMBR The Maximum Aggregated uplink and downlink MBRs to beshared across all Non-GBR bearers according to the subscription of theuser. APN-OI Replacement Indicates the domain name to replace the APN OIwhen constructing the PDN GW FQDN upon which to perform DNS queries.This replacement applies for all the APNs in the subscriber's profile.RFSP Index An index to specific RRM configuration in the E-UTRANURRP-MME UE Reachability Request Parameter indicating that UE activitynotification from MME has been requested by the HSS. CSG SubscriptionData The CSG Subscription Data is a list of CSG IDs per PLMN and foreach CSG ID optionally an associated expiration date which indicates thepoint in time when the subscription to the CSG ID expires; an absentexpiration date indicates unlimited subscription.

Each subscription profile contains one or more PDN subscriptioncontexts: Context Identifier Index of the PDN subscription context. PDNAddress Indicates subscribed IP address(es). PDN Type Indicates thesubscribed PDN Type (IPv4, IPv6, IPv4v6) APN-OI Replacement APN levelAPN-OI Replacement which has same role as UE level APN-OI Replacementbut with higher priority than UE level APN-OI Replacement. This is anoptional parameter. When available, it shall be used to construct thePDN GW FQDN instead of UE level APN-OI Replacement. Access Point Name(APN) A label according to DNS naming conventions describing the accesspoint to the packet data network (or a wildcard) (NOTE 6). EPSsubscribed QoS profile The bearer level QoS parameter values for thatAPN's default bearer (QCI and ARP) (see clause 4.7.3).Subscribed-APN-AMBR The maximum aggregated uplink and downlink MBRs tobe shared across all Non-GBR bearers, which are established for thisAPN. EPS PDN Subscribed The charging characteristics of this PDNSubscribed context Charging Characteristics for the MS, e.g. normal,prepaid, flat-rate, and/or hot billing subscription. The chargingcharacteristics is associated with this APN. VPLMN Address AllowedSpecifies whether for this APN the UE is allowed to use the PDN GW inthe domain of the HPLMN only, or additionally the PDN GW in the domainof the VPLMN. PDN GW identity The identity of the PDN GW used for thisAPN. The PDN GW identity may be either an FQDN or an IP address. The PDNGW identity refers to a specific PDN GW. PDN GW Allocation TypeIndicates whether the PDN GW is statically allocated or dynamicallyselected by other nodes. A statically allocated PDN GW is not changedduring PDN GW selection. PLMN of PDN GW Identifies the PLMN in which thedynamically selected PDN GW is located. Homogenous Support of IMSIndicates whether or not “IMS Voice over PS Sessions” is Over PSSessions for MME supported homogeneously in all TAs in the serving MME.List of APN - PDN GW ID relations (for PDN subscription context withwildcard APN): APN - P-GW relation #n The APN and the identity of thedynamically allocated PDN GW of a PDN connection that is authorised bythe PDN subscription context with the wildcard APN. The PDN GW identitymay be either an FQDN or an IP address. The PDN GW identity refers to aspecific PDN GW.

The above enhancements in the user's subscription record stored in theHSS are advantageous, in particular due to their ability to assist theMobility Management Entity (MME) in deciding whether the user can begranted access to the requested packet data network via Local IP Access(LIPA).

The invention is not limited to the above described exemplaryembodiments, and also encompasses many different variants. Inparticular, most embodiments have been described in the context ofE-UTRAN (with a HeNB), but can be adapted in straight-forward manner toa UTRAN context (with a HNB connecting to the Evolved Packet Core EPC,the EPC network supporting a S4-SGSN node described in 3GPP TS 23.401“Evolved Packet Core architecture for 3GPP accesses; Stage 2”. Anexample of equivalent LIPA architecture for HNB femtocells is shown onFIG. 16.

The following is the summary of modifications compared to thearchitecture for HeNB femto cells described in FIG. 1.

HeNB and MME are replaced by HNB and SGSN, respectively. An extra nodereferred to as HNB GW (specified in 3GPP TS 25.467 “UTRAN architecturefor 3G Home Node B (HNB); Stage 2”) is added, and is connected to theHNB and the SGW via the Iuh and the S12 reference point, respectively.The S11 interface is replaced by an S4 interface. The S5 PGW TEID or theS5 PGW GRE parameter is carried within the RAB ASSIGNMENT REQUESTmessage (defined in 3GPP TS 25.413 “RANAP protocol”). On the Iuinterface, the L-GW address is carried within the INITIAL UE MESSAGEmessage (defined in 3GPP TS 25.413). On the Iuh interface, the L-GWaddress is carried within the HNB REGISTER REQUEST message (defined in3GPP TS 25.467). Alternatively (but less efficiently), the L-GW addressis carried within the UE REGISTER REQUEST message (defined in 3GPP TS25.467).

In a possible embodiment, for the purpose of Lawful Intercept, a copy ofeach uplink IP packet is forwarded across Iuh/S12. The user planeprotocol being the same as in the S1-U case (i.e. GTP-U), the new tag inthe GTP-U encapsulation described earlier is exactly the same. UESPECIFIC INFORMATION INDICATION message (defined in 3GPP TS 25.413) canbe used (instead of the UE CONTEXT MODIFICATION REQUEST message) to turnthe Lawful Intercept feature on or off.

More generally, the invention is applicable to other wirelesstechnologies such as WCDMA, GSM, CDMA2000, TD-SCDMA, or WiMAX. Thevocabulary used in the described embodiment is the conventionalvocabulary in the context of LTE, however other standards use adifferent terminology. The invention is not limited to LTE by the use ofLTE vocabulary. For example the GSM standard refers to “mobile stations”comprising a “mobile equipment” (typically a cell phone) equipped with aSIM card. Despite the fact that the described embodiments commonly referto a “user equipment”, any communication device compliant with therequirement laid out in relation with said embodiments is appropriate,even a GSM compliant communication device.

The invention claimed is:
 1. A method for providing Local IP Access(LIPA), the method performed by an apparatus including a base station(BS) collocated with a local gateway (L-GW), comprising: receiving arequest message comprising a correlation identification (ID) from amobility management entity (MME); determining a destination of an uplinktraffic associated with the BS by using the correlation ID, thecorrelation ID comprising a General Packet Radio Service (GPRS)Tunneling Protocol (GTP) based endpoint identifier of an S5 interface ora Generic Routing Encapsulation (GRE) key of the S5 interface, the S5interface being configured at the L-GW; and if the BS establishes asecure link with a security gateway (SeGW), the L-GW uses a same securelink, and different IP addresses are allocated to the BS and the L-GW,discriminating a data packet delivered through the secure link to the BSand the L-GW by using the different IP addresses.
 2. The method of claim1, wherein the uplink traffic is determined to be forwarded to the L-GWwhen the correlation ID is received.
 3. The method of claim 1, whereinthe S5 interface is configured to be between the L-GW and a servinggateway (S-GW).
 4. The method of claim 1, further comprising, if the BSand the L-GW GW use the same secure link with the SeGW, and a single IPaddress is allocated to the BS and the L-GW, discriminating the datapacket delivered through the secure link to the BS and the L-GW by usingdifferent tunneling endpoint IDs (TEIDs) allocated to the BS and theL-GW.
 5. The method of claim 1, wherein the request message is used forcreating a bearer with a mobile terminal.
 6. The method of claim 1,wherein the request message comprises a bearer setup request message. 7.The method of claim 6, wherein the bearer setup request messagecomprises a Packet Data Network (PDN) connectivity Accept message.
 8. Anapparatus in a communication system, comprising: a local gateway (L-GW)providing Local IP Access (LIPA); a base station (BS) collocated withthe L-GW; and a processor coupled to the L-GW and the BS, and configuredto: receive a request message comprising a correlation identification(ID) from a mobility management entity (MME); determine a destination ofan uplink traffic associated with the BS by using the correlation ID,the correlation ID comprising a General Packet Radio Service (GPRS)Tunneling Protocol (GTP) based endpoint identifier of an S5 interface ora Generic Routing Encapsulation (GRE) key of the S5 interface, the S5interface being configured at the L-GW; and if the BS establishes asecure link with a security gateway (SeGW), the L-GW uses a same securelink, and different IP addresses are allocated to the BS and the L-GW,discriminate a data packet delivered through the secure link to the BSand the L-GW by using the different IP addresses.
 9. The apparatus ofclaim 8, wherein the uplink traffic is determined to be forwarded to theL-GW when the correlation ID is received.
 10. The apparatus of claim 8,wherein the S5 interface is configured to be between the L-GW and aserving gateway (S-GW).
 11. The apparatus of claim 8, wherein, if the BSand the L-GW use the same secure link with the SeGW, and a single IPaddress is allocated to the BS and the L-GW, the processor is furtherconfigured to discriminate the data packet delivered through the securelink to the BS and the L-GW by using different tunneling endpoint IDs(TEIDs) allocated to the BS and the L-GW.
 12. The apparatus of claim 8,wherein the request message is used for creating a bearer with a mobileterminal.
 13. The apparatus of claim 8, wherein the request messagecomprises a bearer setup request message.
 14. The apparatus of claim 13,wherein the bearer setup request message comprises a Packet Data Network(PDN) connectivity Accept message.